A display controller effects the generation of a visual graphic or alphanumeric image on a display "screen" in response to external input of information. The display can take any desirable form, such as a CRT, an LCD, or a gas plasma panel. A typical controller automatically repeatedly retrieves from memory image data that has been input and stored therein by external circuitry and uses the retrieved image data to automatically form and refresh the image on the display "screen." A controller for a bit-mapped display fetches from memory the patterns for each dot on a line of the display and sends it to the display; at the end of a line automatically generates a horizontal sync or latch pulse; repeats these two steps for each line automatically, i.e., without external stimulus; and at the end of the last line automatically generates a vertical sync or frame restart pulse and then starts the process all over again.
A display controller may constitute a significant portion of the cost of equipment that includes the display and its controller, such as a telecommunications terminal. From a competitive standpoint, it is therefore desirable to implement the controller as inexpensively as possible.